Calculation of suction capacity of centrifugal pumps

Information about cavitation characteristics of centrifugal pumps and critical cavitation conditions is given. Depending on the position of the leading edge, impellers are divided into three groups. The spatial lattice of the impeller is presented as a set of elementary lattices on the axisymmetric surfaces of a current of equal-velocity meridional flow. Equations have been derived from the determination of the cavitation margin and the equation of the energy in relative motion for the critical cavitation margin containing a cavitation coefficient referred to the impeller inlet. General equations have been obtained for the critical cavitaion coefficient of specific speed, which can be used to analyze the influence of geometric and operating conditions on the suction capacity of centrifugal impellers, which must be taken into account in designing them. The selection of the typical inlet diameter of the impeller has been substantiated and the critical cavitation coefficients of the elementary lattices have been found. An empirical equation, valid in the whole range of parameters encountered in practice, has been derived for the cavitation coefficient of type-3 impellers with a leading edge located roughly on the diameter of the impeller neck. An analytical equation, applicable for type-1 and-2 impellers, is given for the critical cavitation coefficient with empirical force coefficient values. A scheme for calculation of the suction capacity of such impellers is presented.     

DNA vaccination against Theiler''s murine encephalomyelitis virus leads to alterations in demyelinating disease

Using glycerinated spasmoneme of giant Zoothamnium sp., the physical properties of spasmoneme before and after Ca2+-induced contraction (pCa 4.5) were investigated. The volume change of spasmoneme contraction was measured under zero tension. The length and diameter decreased by about 50% of their initial value as a result of contraction, which means that contraction is nearly isotropic. Thus the volume of spasmoneme decreased drastically by 86% of its original value. The swollen ratio of extended and contracted spasmoneme were 0.07 and 0.37, respectively. Tension-extension relationships of extended and contracted spasmonemes were measured. By applying the theory of rubber elasticity, the number of segments of a chain in originally extended spasmoneme was only 3.3, i.e., the chain was almost a straight one. On the other hand, the number of segments of a chain in contracted spasmoneme was more than 100, i.e., the chain was essentially a random one. Furthermore, the total number of chains in single spasmoneme was the same in extended and contracted spasmoneme. This means that the interchain cross-links of chains were not influenced by addition or removal of Ca2+. Moreover, the molecular weight of a chain is estimated to be at most about 50 kd. By considering all these results, it is concluded that the contractile mechanism of spasmoneme originates in the intramolecular folding and unfolding induced by Ca2+ binding and detaching.     

The Effect of External Electrostatic Field Orientation on Aerosol Filtration by Granular Filters

The separation of fine aerosol particles by a packed granular-bed filter, enhanced by external electrostatic fields, was studied experimentally and theoretically. The filtration efficiencies of charged and neutralized aerosols were measured for external fields aligned with the air flow, transverse to the flow, and opposite to the flow. Theoretical models of electrostatically enhanced granular-bed filtration of micrometer and submicrometer particles were developed. Experimental results which demonstrate the relative merit of each configuration were presented and compared with the theory. The parallel-field configuration yielded the best filtration efficiency followed by the transverse configuration.     

Calendar of meetings

The kinetics of the thermal decomposition of the crystalline poly(1,6-di-N-carbazolyl-2,4-hexadiyne) prepared by γ-radiation induced polymerisation were studied over the temperature range 380-450°C by means of a flow system, coupled to a gas chromatograph. Two major volatile reaction products were found: carbazole and 9-methylcarbazole, leaving behind a carbonaceous residue. The reaction was found to be complex with two autoacceleratory regions followed by a very slow limiting rate after 65% weight loss. Whereas the magnitude of the first of these regions was found to be dependent on factors influencing the level of crystal purity and perfection, the second region was independent of these. A reaction mechanism is proposed, based on initiation by stress-induced shearing of sidegroups, followed by concurrent molecular/radical non-chain processes. The kinetics of the decomposition were found to be best described by the Avrami-Erofeyev equation, and the Arrhenius parameters were determined for both autoacceleratory processes.     

Characterization of circulating erythrocytes from myelodysplastic patients treated with recombinant human erythropoietin

Age-density fractionation, in-vitro erythrophagocytosis, and enumeration of membrane-bound antibodies were monitored for circulating red blood cells (RBC) from five anemic patients with myelodysplastic syndromes (MDS), in relation to administration of recombinant human erythropoietin (rhEPO). The density distribution patterns of erythrocytes from the patients prior to treatment were in accordance with their inability to produce compensating levels of circulating RBC. The complete response of one patient to rhEPO and partial responses of two other patients were accompanied by shifts to larger proportions of low density (young) RBC. In vitro phagocytosis of density-fractionated RBC from the complete responder was similar to those of age-matched non-anemic donors. Elevated erythrophagocytosis prior to rhEPO administration was observed for the partial responders and further increased during treatment in one, suggesting the stimulation of abnormal progenitors producing highly defective erythrocytes. There was no correlation between levels of erythrophagocytosis and RBC membrane-bound immunoglobulins in this group of patients. Our findings suggest that density distribution analysis of circulating RBC coupled with in vitro erythrophagocytosis may provide useful predictive tools for selecting potential responders to rhEPO administration among anemic MDS patients.     

Participation of phosphoinositide-specific phospholipase Cgamma1 and STAT1 protein in the formation of latent complexes of signal proteins

It is known that the growth factor activates appropriate membrane receptors which become starting points of cascades of protein-protein interactions leading to cellular response. Recent data suggest that different signalling pathways may cross-talk during the cellular response. Here we show that phosphoinositide-specific phospholipase C gamma 1, one of the key elements in phosphoinositide pathway of signal transduction, is physically associated with members of the STAT pathway. The precipitation of phospholipase C gamma 1, using polyclonal antibody in A-431 cells, leads to co-immunoprecipitation of STAT1 alpha and STAT1 beta, as well as STAT3. The formation of such complexes was observed in both unstimulated and EGF stimulated cells. The participation of SH3-domains in the formation of such complexes is discussed.     

Shape estimation from topographic primal sketch

In this paper, a technique for estimating object shape from topographic primal sketch is investigated. Given a gray tone image of a three-dimensional object, a topographic labeling of the image indicates the peaks and pits, ridges and valleys, and flats and hillsides of the underlying, continuous, gray tone surface. The patterns of these topographic labels capture information about the original three-dimensional object in the scene and about the illumination. In order to determine if estimation of three-dimensional shape from a topographic labeling is feasible, we have both analytically and experimentally determined the topographic labelings for images of some mathematically generated surfaces with varied directions of illumination. Our results indicate that such patterns do exist and will be useful in determining three-dimensional shape from two-dimensional images. A scheme for partial classification of three-dimensional object surface is proposed. Preliminary results are illustrated.     

Synthesis and in vitro antimalarial activity of sulfone endoperoxides

A series of 4,8-dimethyl-4-phenylsulfonylmethyl-2,3-dioxabicyclo[3.3.1]+ ++nonanes, carrying a variety of substituents at position-8 (4) were prepared by a short and efficient method from R-(+)-limonene. Key reactions include thiol oxygen cooxidation, and alkylation and acylation of a sterically hindered tertiary alcohol compatible with the endoperoxy functionality. Some of compounds 4, which are structurally related to yingzhaosu A (2), were found to exhibit in vitro antimalarial activity comparable to that of artemisinin (1) and superior to that of arteflene (3).